Mechanical movement transmitting apparatus



13, 1934. P. K. MCGALL 1,950,857

MECHANICAL MOVEMENT TRANSMITTING APPARATUS Filed March 23, 1931 2Sheets-Sheet l ATTORNEY March 13, 1934. P. K. M GALL MECHANICAL MOVEMENTTRANSMITTING APPARATUS Filed March 23, 1931 2 Sheets-Sheet 2 INQENTORATTORN EY Patented Mar. 13, 1934 UNITED STATES PATENT orrice MECHANICALMOVEMENT TRANSMITTING APPARATUS Philip K. McGall, Orange, N. J.,assignor Best Manufacturing Company, Irvington, N. .L, a

copartnership The present invention relates to apparatus for thetransmission of motion by mechanical means and particularly with thetransmission of vibrational movement as, for instance, vibrationalmovement derived from the armature of a loud speaker motor, and has todo specifically with the transmission of such vibrational movement sothat its angle or direction of application may be changed or redirectedas desired, so

that its line of application may be translated or displaced bodily asdesired, and so that the amplitude of the vibrations may be amplified orreduced.

The invention is particularly adaptable to it loud speaker construction,and it has as a broad object and advantage the possibility of mountingthe sound radiating diaphragm and the loud speaker motor in suchrelative positions as desired, thus avoiding certain importantstructural limitations which are encountered in the usual loud speakerconstruction. As a specific illustration, the present invention makes itpossible to design loud speakers of particularly compact assembly and ofparticularly small over-all dimensions without sacrifice of quality ofsound reproduction.

In loud speaker operation, an armature or movable vibratory element isvibrated under the influence of the energizing electrical forces 80which are applied to the loud speaker motor from a radio set, amplifier,or the like, and the resulting vibrational movement of the armature istransmitted to a sound radiating diaphragm through the medium of adriving rod or other appropriate mechanical connection to therebyvibrate the diaphragm and eflfect generation of sound in volumesufficient to be heard throughout a room. The modern tendency in loudspeaker construction is toward a reduction in size of the loud speaker.This is particularly true with loud speakers designed for installationin small cabinets, automobiles, hotel rooms where the loud speaker isplaced in the wall, and the like.

It is an object of this invention to provide mechanical movementtransmitting apparatus, adapted particularly for loud speakers andsimilar uses, wherein the vibrational movement generated by the armatureof the loud speaker motor is transmitted positively and withoutdistortion to a driving element located entirely independently of thelocation or direction of movement of the vibrating element.

The construction and combination of parts by means of which the abovestated and other objects and advantages are obtained are described belowand are illustrated in the accompanying drawings wherein a preferredembodiment of the invention as applied to a loud speaker is shown. Inthe drawings, Figure 1 is a face view showing a cone type loud speakerwhich embodies the present invention; Figure 2 is a transverse sectionalview taken on the plane indicated at 2-2 on Figure 1; Figure 3 is apartial sectional view taken as indicated at 88 3-3 on Figure 2; andFigure 4 is a perspective view illustrating certain details of themovement transmitting apparatus of the invention.

Referring to the drawings, 1 indicates the sound radiating diaphragm ofthe loud speaker, to here shown as a cone type diaphragm which may bemade of paper, fabric, or other suitable material. The diaphragm l issupported at its periphery and is substantially enclosed by a housing 2,as shown. The loud speaker motor m for purposes of illustration, isshown as a socalled magnetic type of motor which comprises a permanentmagnet 5 having pole pieces 6 between which an armature 7 operates, the

armature being in the field of the permanent magnet 5 and being also inthe field produced by coil 8 which surrounds the armature '7, as shown,and which is supplied through its terminals 9 with energizing currentfrom the radio set, amplifier, or the like. The loud speaker at motor ismounted on supporting bars 10 which extend across the open face of thecone as shown, the arrangement being such that the loud speaker motorlies entirely within the cone 1 so that the entire speaker occupies onlyas much as does 00 the diaphragm 1 alone. Armature 7 operates in the airgap between pole pieces 6 and, in regular operation of the apparatus,undergoes a vibrational movement about its longitudinal axis representedby armature mounting springs 11.

In the embodiment of the invention here shown, as illustratedparticularly in Figure 4, a driving rod 12 is connected at one end toarmature '7, as shown, so that vibration of the armature efiectslongitudinal vibratory movement of the rod 12. At its other end drivingrod 12 is connected to a crank arm 14 here shown as a die-stamped memberof sheet metal soldered or otherwise suitably secured to a shaft 15, asindicated at 16, with its free end furnishing the connection withthelink 12, as shown.

Shaft 15 consists of a hollow light-walled metal tube. Shaft 15, beinghollow, is possessed of maximum stifiness for a given weight, thusavoiding objectionable transverse vibration. Be-

ing of thin, light metal, shaft 15 is of low mass and thus avoidsdistortion of reproduced sound due to excessive inertia. A flat spring17 is secured to one end of the hollow shaft 15, the spring 17 being setinto the end of shaft 15 preferably across a diameter of the shaft asshown. The spring 17 is short and is secured to the supporting framebars 10 by means of any appropriate connection such as the screwconnection indicated at 18. At the other end of shaft 15 a. second flatspring 19 is secured, this spring also preferably being set into the endof shaft 15 across a diameter thereof, the spring 19 being preferablyarranged, as shown, across a diameter of the shaft 15 which is at rightangles to the other spring 17 thereby to aid in avoiding objectionableresonance points. The outer end of spring 19 is attached by a screwconnection 20 to a cylindrical adjusting member 21. Adjusting member 21lies in a bore provided in a block 22, the block 22 being split asindicated at'23 and provided with a tightening screw 24 by means ofwhich block 23 may be clamped down upon adjusting member 21 to lock itin any desired position of adjustment, all of which will be evident fromthe drawings.

Adjusting member 21 is slotted at its outer end as indicated at 25 sothat, by means of a screw driver or other adjusting tool, it can beturned within block 22 to place springs 17 and 19 under such tension asmay be desired for proper operation of the apparatus. A particularadvantage of adjusting block, 21 and its slot 25 which is accessiblewith an ordinary screw driver after the apparatus is completelyassembled, is in the centering of armature 7. After assembly of theapparatus, armature 7 must be adjusted in the air gap between polepieces 6 so that it lies centrally in the gap out of contact with eachpole piece. The magnetic attraction of the pole pieces tends to pull thearmature over against one or the other of the pole pieces, and.

hence springs 17 and 19 must be tensioned in order to hold the armature7 in proper neutral position in the air gap. Proper tensioning of the,springs and proper centering of the armature is effected by means ofadjusting block 21 after assembly of the apparatus is completed. Pads17a and 19a of heavy rubber are preferably forced over springs 17 and19, as shown, to aid in preventing excessive vibration.

Hollow shaft 15 is provided with a second crank arm 26 which, in theembodiment here shown, extends off the shaft 15 at right angles to crankarm 14. .Crank arm 26 is secured to a driving rod or link 27, asindicated at 28, and the opposite end of link 27 is secured to the soundradiating cone 21 as indicated at 29. It will be understood that thelength of shaft 15 may be limited, if desired, to the desired distancebetween crank arms 14 and 26, to minimize the total mass of movingparts. This could be effected in the structure here shown by movingsupporting bar 10 over adjacent crank arm 26 or by providing anothersupporting bar for the purpose.

The operation of the device is as follows: Armature 7 vibrates under theinfluence of the energizing electric current which is supplied to theloud speaker motor. The vibrations of the armature are transmittedthrough connecting link 12 to crank arm 14, with the result that theshaft 15 is given a vibrating movement about its longitudinal axisagainst-the action of springs 17 and 19. This rotational vibrationmovement of shaft 15 actuates crank arm 26 which in turn vibratesdriving rod 27 and thereby actuates the sound radiating cone 1. In theparticular embodiment here shown the direction of vibration of armature7 has been turned through a right angle, has been translated into a newplane removed from the initial driving rod 12 a distance equal to thedistance between crank arms 14 and 26, and has been increased inamplitude by an amount equal to the ratio of the effective moment arm ofcrank arm 26 to that of. crank arm 14. I

This arrangement shown and described herein permits the magnet 5 of theloud speaker motor to lie within the cone diaphragm, thus affording aparticularly compact assembly and giving a complete speaker which is nolarger than the diaphragm itself. If the driving rod 12, or a rodparallel to it, were secured directly to the cone 1, the loud speakermotor could not be contained within the confines of the cone diaphgram.Likewise, if the driving rod 27 were not displaced as shown from drivingrod 12, the loud speaker motor would have to be shifted .relative to theaxis of the cone so that armature 7 lay on the axis of the cone, inwhich case the motor could not be contained within the confines of thecone. The present invention is, therefore, important in the manufactureof small speakers of all kinds, such as wall type speakers, cabinetspeakers, and the like.

It will be understood that crank arms 14 and 26 can be secured to shaft15 at any desired relative angular relation, thereby effectingtranslation of the direction of application of the vibrational movementthrough any desired angle. It will also be. understood that the spacingof crank arms 16 and 26 along the length of the shaft may be regulatedas desired depending on how far from the original plane of motion it isdesired to translate the applied motion which is carried by driving rod27. If only a short distance of translation along the length of the axisof the shaft is desired, the shaft may well be short and might evenassume the form of a drum or disk or wheel as distinguished from anelongated shaft. It will be further noted that the relation between themoment arms represented by crank arm 14 and crank arm 26 may be variedas desired to determine the amplitude of the vibration applied to soundradiating cone '1 relative to the amplitude of vibration represented bythe actual movement or" the armature 7. v

While the invention has been described herein as applied to a particularform of loud speaker it will be understood that it is applicable toother types of loud speakers, including the socalled dynamic type ofloud speaker, and is also applicable to various other uses where achange in the direction of application, a shifting of the line ofapplication, or a change in amplitude of a vibrational movement isdesired.

The invention is defined in the appended claims largely in terms-of thefeatures of structure, design, combination and arrangement which areresponsible for the above described advantages, and variations from thespecific disclosure of the specification and drawings may be made withinthe scope of the claims without departing from the invention.

I claim:

1. Motion transmitting apparatus of the class described which comprisesa shaft, supports arranged adjacent the respective ends of said shaft, aspring interposed between each of said supports and the adjacent end ofsaid shaft, whereby partial rotation of said shaft against the tensionof said springs is permitted resilient members lying closely adjacentsaid respec-- tive springs for preventing objectionable vibrationthereof, a vibrating actuating element, connections between saidactuating element and said shaft for effecting vibrational rotativemovement thereof against the tension of said springs, and connectionsbetween said rotative member and an actuated member for impartingvibrational movement thereto.

2. A loud speaker construction which comprises a cone type soundradiating diaphragm, a loud speaker motor mounted within the con-"fines'of said diaphragm, and means for translating vibratory motionfrom the armature of the loud speaker motor into a direction parallelwith the axis of the cone and coincident therewith which comprises aconnecting link secured to the motor armature, a rotatable shaftextending substantially at right angles to the axis of said cone, acrank arm provided on said shaft, connections between said driving linkand said crank arm for imparting rotary vibrational movement to saidshaft, a driving rod for said cone substantially coincident with theaxis thereof, and a second crank arm connected to said shaft and to saiddriving rod, whereby a loud speaker motor of substantial size can becontained within the confines of the sound radiating cone.

' PHILIP K. McGALL.

